1. Field of the Invention
The present invention relates to an electronic balance which includes a plurality of Roberval's chains.
2. Discussion of the Background
Many of conventional electronic balances and scales utilize a Roberval's chain (also called a "parallel guide") to support a balance pan in order to limit the movement of the balance pan on which a mass is placed. The Roberval's chain includes a fixed pillar, a movable pillar, and upper and lower beams. The fixed pillar is fixed to or integrated into a frame of the scale. The movable pillar is supported by the fixed pillar via the upper and lower beams which are substantially in parallel with each other. Each beam is connected to the fixed pillar at one end and to the movable pillar at the other end through each fulcrum. The movable pillar supports the balance pan. Thus, the load applied to the balance pan is transmitted to an electric load detector through the movable pillar and a lever.
Japanese Unexamined Utility Model Publication (Kokai) No. 63-35,924 discloses a Roberval's chain which is constructed by assembling separate pieces of a fixed pillar, a movable pillar, and upper and lower beams. Japanese Unexamined Patent Publication (Kokai) No. 63-277,936 discloses a Roberval's chain which has a single piece construction carved out from a single flat plate. The contents of these references are incorporated herein by reference in their entirety.
In these balances, however, it is difficult to make an adjustment because an adjustment of an offset error in the longitudinal direction of the upper and lower beams affects an offset error in the transverse direction of the upper and lower beams or vise versa.